The present invention relates to the art of telescoping masts and more particularly to a telescoping mast having a rigid drive assembly for telescoping mast sections to any position between fully retracted and fully extended heights.
Quick erecting telescoping masts are used for many applications including civilian, industrial and military applications throughout the world. Quick erecting telescoping masts are particularly suited for applications wherever there is a need for portable masts requiring fast setup and teardowns with minimum power and effort. In addition to numerous military applications, including target acquisition, surveillance and field communications, quick erecting telescoping masts are utilized commercially to support a wide variety of antennas, elevated testing equipment, floodlights and cameras. Free-standing masts can be installed on a wide variety of vehicles and shelters.
Heretofore, telescoping masts have been either pneumatically, hydraulically or chain driven. Pneumatic masts require airtight seals between telescopic mast sections in order to function as intended. However, the environment in which such masts are used makes maintaining an airtight condition between mast sections problematic. Contaminants, or radial ice, deposited between mast sections, or at the junctions will stop the mast from descending or cause damage to the mast sections, and can easily destroy the seal required for efficient operation of the pneumatic mast. In the event that the pneumatic integrity of the seal is destroyed, the mast will come down due to gravity with potentially disastrous consequences.
A further disadvantage to pneumatically powered telescoping masts is that they can only assume one of two positions. Either the masts are fully extended or fully retracted. In many applications, however, because of obstructions or other considerations, it is desirable to have the telescoping mast sections in a partial state of extension or retraction. A further disadvantage with pneumatic masts is that they are relatively heavy in weight, limiting their suitability for vehicle roof applications.
Hydraulic systems for elevating masts suffer from many of the same shortcomings. Hydraulic drives are relatively heavy in weight and are expensive to manufacture, assemble, and maintain. Moreover, such drives are vulnerable to damage from contact with the environment since hydraulic lines are exposed. Additionally, contaminants can infiltrate the hydraulic system and cause malfunction or failure.
Chain driven telescopic masts likewise suffer from the same deficiencies. The drive mechanisms are relatively heavy in weight and are expensive to manufacture, assemble and maintain. The chain link mechanism is also exposed and susceptible to damage from contact with environmental objects.
Telescoping masts have been widely employed for radio antennas, lights and a variety of other fixtures. Such masts have been operated by a variety of mechanisms, including winches, hydraulic systems and the like. More recently, telescoping masts have been devised which use an axial screw mechanism for raising and lowering the mast sections.
When telescoping masts are used under extreme environmental conditions and particularly in military or other portable operations, it is highly desirable that the masts be ruggedly constructed and be extremely fast, reliable and safe to operate. In such portable masts, it is particularly important that the sections be extended and retracted in sequence and that as each section is fully extended it is positively locked to the next lower section. In these ways the mast can be extended to the full desired height and the possibility of accidents and injuries due to one or more of the mast sections suddenly coming down is minimized.
Another complication is encountered when an axial drive screw system is used for raising and retracting a telescoping antenna. The nut-elements carried by each mast section must sequentially engage and disengage the threads of the drive screw as the respective mast sections are raised. Since there will normally be some initial mismatch between the threads of the drive screw and the threads of the nut, axial loadings will temporarily be applied to the drive mechanism until the nuts properly engage the threads of the drive screw. Such axial loadings can damage the drive train components.
Accordingly, there is a need for a mast telescopic system with a locking mechanism which overcomes the above-mentioned defects and others while providing more advantageous overall results.